It quite depends on what you are applying for. As a developer, I would tell them the number of tables, views and stored program units to give them an idea, together with the number of records in the key tables. (eg. number of students for an application tracking course-info)
As a DBA, you'd probably add to that the physical size of the database files.

Quote:

1.how many columns can a table can have and size of the table
2.how many rows of code can a package/procedure/function/trigger have and the size of each

1: quite easy to find if you'd search for that
2: There is no real limit to that. The practical limit would be:
package: none
procedure/function: about 1-2 screens
trigger: as small as possible. (only assign PK-column with sequence)